Dual rate leaf spring construction

Abstract

A dual rate leaf spring construction including a main leaf spring, preferably formed of fiber reinforced resin, and having a central section adapted to be connected to an axle of a vehicle and having a pair of ends to be connected to the frame of the vehicle. A secondary leaf spring, having a substantially shorter length than the main leaf spring, is secured beneath and parallel to the main leaf spring, and an elastomeric pad is mounted on each end of the secondary spring. The pads have upwardly facing rounded heads that are spaced out of contact with the lower surface of the main spring under normal load conditions. Under heavy load conditions, the main spring will deflect downwardly into contact with the pads to thereby enable the secondary spring to carry a portion of the load.

I claim: 
     
       1. A dual rate leaf spring construction, comprising a main leaf spring composed of fiber reinforced thermosetting resin having a central section disposed to be connected to an axle of a vehicle and having a pair of ends disposed to be connected to a frame of said vehicle, a secondary leaf spring disposed beneath the main leaf spring and having a length from 0.25 to 0.75 times the length of the main leaf spring, an elastomeric pad mounted on each end of the secondary leaf spring and having an upwardly extending head, said head having a generally rounded configuration in vertical cross section and each head being spaced out of contact with the lower surface of the main leaf spring under normal load conditions, and connecting means for connecting the central sections of said springs to the axle of said vehicle, said connecting means comprising an axle mounting bracket, a resilient compressible jacket enclosing the central section of said main spring, a channel member surrounding said jacket and having a web portion and a pair of side flanges extending outwardly from said web portion, the ends of said flanges contacting the upper surface of said secondary leaf spring to thereby limit the compression of said jacket, and clamping means for clamping said channel member to said mounting bracket, and the application of a predetermined heavy load to said main leaf spring causing said main leaf spring to be deflected downwardly into engagement with said pads to thereby enable said secondary leaf spring to carry a portion of said heavy load. 
     
     
       2. The leaf spring of claim 1, wherein said secondary leaf spring is composed of steel. 
     
     
       3. The leaf spring construction of claim 1, wherein each end of the secondary leaf spring is provided with a hole and each pad is provided with a projection that is snap fitted within the respective hole. 
     
     
       4. A dual rate leaf spring comprising a generally upwardly curved main leaf spring having a central section disposed to be connected to an axle of a vehicle and having a pair of ends disposed to be connected to a frame of said vehicle, said main spring being composed of a single leaf of fiber reinforced thermosetting resin, a secondary leaf spring disposed beneath the main leaf spring and having a substantially shorter length than the main leaf spring, said secondary spring having a central portion and a pair of end portions extending downwardly and outwardly from said central portion, an elastomeric pad mounted on each end of the secondary leaf spring and having an upwardly projecting head, each head having a generally rounded configuration in vertical cross section and each head being spaced out of contact with the lower surface of the main leaf spring under normal load conditions, and clamping means for clamping the main leaf spring and the secondary leaf spring to said axle, said clamping means including means for spacing said secondary leaf spring from said main leaf spring whereby said secondary spring is spaced out of contact with said main spring throughout its length, the application of a predetermined heavy load to the main leaf spring causing the main leaf spring to be deflected downwardly into engagement with said pads to thereby enable said secondary leaf spring to carry a portion of said load. 
     
     
       5. A dual rate leaf spring comprising a generally upwardly curved main leaf spring having a mounting section disposed to be connected to a vehicle and having a pair of ends, said main spring being composed of a single leaf of fiber reinforced thermosetting resin, a secondary leaf spring disposed beneath the main leaf spring and having a substantially shorter length than the main leaf spring, said secondary spring having a central portion and a pair of end portions extending outwardly from said central portion, an elastomeric pad mounted on each end of the secondary leaf spring and having an upwardly projecting head, each head being spaced out of contact with the lower surface of the main leaf spring under normal load conditions, and clamping means for clamping the main leaf spring and the secondary leaf spring to said vehicle, said clamping means including means for spacing said secondary leaf spring from said main leaf spring whereby said secondary leaf spring is spaced out of contact with said main spring throughout its length, the application of a predetermined heavy load to the main leaf spring causing the main leaf spring to be deflected downwardly into engagement with said pads to thereby enable said secondary leaf spring to carry a portion of said load, each pad being configured to provide a relatively large area of contact between said pad and said main leaf spring under said heavy load.